# -*- coding: utf-8 -*-
# Copyright 2014 OpenMarket Ltd
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

"""This module contains classes for authenticating the user."""

from twisted.internet import defer

from synapse.api.constants import Membership, JoinRules
from synapse.api.errors import AuthError, StoreError, Codes, SynapseError
from synapse.api.events.room import (
    RoomMemberEvent, RoomPowerLevelsEvent, RoomDeletionEvent,
)
from synapse.util.logutils import log_function

import logging

logger = logging.getLogger(__name__)


class Auth(object):

    def __init__(self, hs):
        self.hs = hs
        self.store = hs.get_datastore()

    @defer.inlineCallbacks
    def check(self, event, snapshot, raises=False):
        """ Checks if this event is correctly authed.

        Returns:
            True if the auth checks pass.
        Raises:
            AuthError if there was a problem authorising this event. This will
            be raised only if raises=True.
        """
        try:
            if hasattr(event, "room_id"):
                is_state = hasattr(event, "state_key")

                if event.type == RoomMemberEvent.TYPE:
                    yield self._can_replace_state(event)
                    allowed = yield self.is_membership_change_allowed(event)
                    defer.returnValue(allowed)
                    return

                self._check_joined_room(
                    member=snapshot.membership_state,
                    user_id=snapshot.user_id,
                    room_id=snapshot.room_id,
                )

                if is_state:
                    # TODO (erikj): This really only should be called for *new*
                    # state
                    yield self._can_add_state(event)
                    yield self._can_replace_state(event)
                else:
                    yield self._can_send_event(event)

                if event.type == RoomPowerLevelsEvent.TYPE:
                    yield self._check_power_levels(event)

                if event.type == RoomDeletionEvent.TYPE:
                    yield self._check_deletion(event)

                defer.returnValue(True)
            else:
                raise AuthError(500, "Unknown event: %s" % event)
        except AuthError as e:
            logger.info("Event auth check failed on event %s with msg: %s",
                        event, e.msg)
            if raises:
                raise e
        defer.returnValue(False)

    @defer.inlineCallbacks
    def check_joined_room(self, room_id, user_id):
        try:
            member = yield self.store.get_room_member(
                room_id=room_id,
                user_id=user_id
            )
            self._check_joined_room(member, user_id, room_id)
            defer.returnValue(member)
        except AttributeError:
            pass
        defer.returnValue(None)

    def _check_joined_room(self, member, user_id, room_id):
        if not member or member.membership != Membership.JOIN:
            raise AuthError(403, "User %s not in room %s (%s)" % (
                user_id, room_id, repr(member)
            ))

    @defer.inlineCallbacks
    def is_membership_change_allowed(self, event):
        target_user_id = event.state_key

        # does this room even exist
        room = yield self.store.get_room(event.room_id)
        if not room:
            raise AuthError(403, "Room does not exist")

        # get info about the caller
        try:
            caller = yield self.store.get_room_member(
                user_id=event.user_id,
                room_id=event.room_id)
        except:
            caller = None
        caller_in_room = caller and caller.membership == "join"

        # get info about the target
        try:
            target = yield self.store.get_room_member(
                user_id=target_user_id,
                room_id=event.room_id)
        except:
            target = None
        target_in_room = target and target.membership == "join"

        membership = event.content["membership"]

        join_rule = yield self.store.get_room_join_rule(event.room_id)
        if not join_rule:
            join_rule = JoinRules.INVITE

        if Membership.INVITE == membership:
            # TODO (erikj): We should probably handle this more intelligently
            # PRIVATE join rules.

            # Invites are valid iff caller is in the room and target isn't.
            if not caller_in_room:  # caller isn't joined
                raise AuthError(403, "You are not in room %s." % event.room_id)
            elif target_in_room:  # the target is already in the room.
                raise AuthError(403, "%s is already in the room." %
                                     target_user_id)
        elif Membership.JOIN == membership:
            # Joins are valid iff caller == target and they were:
            # invited: They are accepting the invitation
            # joined: It's a NOOP
            if event.user_id != target_user_id:
                raise AuthError(403, "Cannot force another user to join.")
            elif join_rule == JoinRules.PUBLIC or room.is_public:
                pass
            elif join_rule == JoinRules.INVITE:
                if (
                    not caller or caller.membership not in
                    [Membership.INVITE, Membership.JOIN]
                ):
                    raise AuthError(403, "You are not invited to this room.")
            else:
                # TODO (erikj): may_join list
                # TODO (erikj): private rooms
                raise AuthError(403, "You are not allowed to join this room")
        elif Membership.LEAVE == membership:
            # TODO (erikj): Implement kicks.

            if not caller_in_room:  # trying to leave a room you aren't joined
                raise AuthError(403, "You are not in room %s." % event.room_id)
            elif target_user_id != event.user_id:
                user_level = yield self.store.get_power_level(
                    event.room_id,
                    event.user_id,
                )
                _, kick_level, _ = yield self.store.get_ops_levels(event.room_id)

                if kick_level:
                    kick_level = int(kick_level)
                else:
                    kick_level = 50

                if user_level < kick_level:
                    raise AuthError(
                        403, "You cannot kick user %s." % target_user_id
                    )
        elif Membership.BAN == membership:
            user_level = yield self.store.get_power_level(
                event.room_id,
                event.user_id,
            )

            ban_level, _, _  = yield self.store.get_ops_levels(event.room_id)

            if ban_level:
                ban_level = int(ban_level)
            else:
                ban_level = 50  # FIXME (erikj): What should we do here?

            if user_level < ban_level:
                raise AuthError(403, "You don't have permission to ban")
        else:
            raise AuthError(500, "Unknown membership %s" % membership)

        defer.returnValue(True)

    def get_user_by_req(self, request):
        """ Get a registered user's ID.

        Args:
            request - An HTTP request with an access_token query parameter.
        Returns:
            UserID : User ID object of the user making the request
        Raises:
            AuthError if no user by that token exists or the token is invalid.
        """
        # Can optionally look elsewhere in the request (e.g. headers)
        try:
            return self.get_user_by_token(request.args["access_token"][0])
        except KeyError:
            raise AuthError(403, "Missing access token.")

    @defer.inlineCallbacks
    def get_user_by_token(self, token):
        """ Get a registered user's ID.

        Args:
            token (str)- The access token to get the user by.
        Returns:
            UserID : User ID object of the user who has that access token.
        Raises:
            AuthError if no user by that token exists or the token is invalid.
        """
        try:
            user_id = yield self.store.get_user_by_token(token=token)
            if not user_id:
                raise StoreError()
            defer.returnValue(self.hs.parse_userid(user_id))
        except StoreError:
            raise AuthError(403, "Unrecognised access token.",
                            errcode=Codes.UNKNOWN_TOKEN)

    @defer.inlineCallbacks
    @log_function
    def _can_send_event(self, event):
        send_level = yield self.store.get_send_event_level(event.room_id)

        if send_level:
            send_level = int(send_level)
        else:
            send_level = 0

        user_level = yield self.store.get_power_level(
            event.room_id,
            event.user_id,
        )

        if user_level:
            user_level = int(user_level)
        else:
            user_level = 0

        if user_level < send_level:
            raise AuthError(
                403, "You don't have permission to post to the room"
            )

        defer.returnValue(True)

    @defer.inlineCallbacks
    def _can_add_state(self, event):
        add_level = yield self.store.get_add_state_level(event.room_id)

        if not add_level:
            defer.returnValue(True)

        add_level = int(add_level)

        user_level = yield self.store.get_power_level(
            event.room_id,
            event.user_id,
        )

        user_level = int(user_level)

        if user_level < add_level:
            raise AuthError(
                403, "You don't have permission to add state to the room"
            )

        defer.returnValue(True)

    @defer.inlineCallbacks
    def _can_replace_state(self, event):
        current_state = yield self.store.get_current_state(
            event.room_id,
            event.type,
            event.state_key,
        )

        if current_state:
            current_state = current_state[0]

        user_level = yield self.store.get_power_level(
            event.room_id,
            event.user_id,
        )

        if user_level:
            user_level = int(user_level)
        else:
            user_level = 0

        logger.debug(
            "Checking power level for %s, %s", event.user_id, user_level
        )
        if current_state and hasattr(current_state, "required_power_level"):
            req = current_state.required_power_level

            logger.debug("Checked power level for %s, %s", event.user_id, req)
            if user_level < req:
                raise AuthError(
                    403,
                    "You don't have permission to change that state"
                )

    @defer.inlineCallbacks
    def _check_deletion(self, event):
        user_level = yield self.store.get_power_level(
            event.room_id,
            event.user_id,
        )

        if user_level:
            user_level = int(user_level)
        else:
            user_level = 0

        _, _, delete_level  = yield self.store.get_ops_levels(event.room_id)

        if not delete_level:
            delete_level = 50

        if user_level < delete_level:
            raise AuthError(
                403,
                "You don't have permission to delete events"
            )

    @defer.inlineCallbacks
    def _check_power_levels(self, event):
        for k, v in event.content.items():
            if k == "default":
                continue

            # FIXME (erikj): We don't want hsob_Ts in content.
            if k == "hsob_ts":
                continue

            try:
                self.hs.parse_userid(k)
            except:
                raise SynapseError(400, "Not a valid user_id: %s" % (k,))

            try:
                int(v)
            except:
                raise SynapseError(400, "Not a valid power level: %s" % (v,))

        current_state = yield self.store.get_current_state(
            event.room_id,
            event.type,
            event.state_key,
        )

        if not current_state:
            return
        else:
            current_state = current_state[0]

        user_level = yield self.store.get_power_level(
            event.room_id,
            event.user_id,
        )

        if user_level:
            user_level = int(user_level)
        else:
            user_level = 0

        old_list = current_state.content

        # FIXME (erikj)
        old_people = {k: v for k, v in old_list.items() if k.startswith("@")}
        new_people = {
            k: v for k, v in event.content.items()
            if k.startswith("@")
        }

        removed = set(old_people.keys()) - set(new_people.keys())
        added = set(old_people.keys()) - set(new_people.keys())
        same = set(old_people.keys()) & set(new_people.keys())

        for r in removed:
            if int(old_list.content[r]) > user_level:
                raise AuthError(
                    403,
                    "You don't have permission to remove user: %s" % (r, )
                )

        for n in added:
            if int(event.content[n]) > user_level:
                raise AuthError(
                    403,
                    "You don't have permission to add ops level greater "
                    "than your own"
                )

        for s in same:
            if int(event.content[s]) != int(old_list[s]):
                if int(event.content[s]) > user_level:
                    raise AuthError(
                        403,
                        "You don't have permission to add ops level greater "
                        "than your own"
                    )

        if "default" in old_list:
            old_default = int(old_list["default"])

            if old_default > user_level:
                raise AuthError(
                    403,
                    "You don't have permission to add ops level greater than "
                    "your own"
                )

            if "default" in event.content:
                new_default = int(event.content["default"])

                if new_default > user_level:
                    raise AuthError(
                        403,
                        "You don't have permission to add ops level greater "
                        "than your own"
                    )